How to migrate Nextcloud Docker to a new machine

I have a Nextcloud installation on a server that was installed using docker-compose. This installation utilizes a Nextcloud docker image and a separate MySQL (8.0) docker image for database access. The data and configuration files are placed in external volumes specified in the docker-compose.yml file.

I have recently put together a new machine that has more memory, a faster CPU, and (most importantly) much more disk space. I would like to migrate my current installation to the new machine.

The actual installation is simple enough: I can simply copy my docker-compose.yml file to the new machine and run it. The problem is with the data and the (somewhat unique) configuration that I have. I would like to get those onto the new machine.

The issue of migrating a dockerized Nextcloud installation has different issues from those associated with migrating a bare-metal or VM installation. For one thing, there is no clear way to place the installation into maintenance mode, you are working with two containers (effectively, this is like coordinating two different machines) and many of the steps described for migrating a bare-metal installation will not work reliably for a containerized installation (yes, one can go into the container to run some of the commands. required, but my attempts to do this resulted in screwed-up migrations).

Doing Google searches, I am seeing plenty of articles and instructions on how to migrate bare-metal Nextcloud installations from one machine to another, and how to migrate bare-metal (and virtual machine) installations to Docker. The procedures are pretty complex and involve placing the installation into maintenance mode and performing various backups and restores. Unfortunately, while I have seen a few people asking about how to migrate dockerized Nextcloud installations, there are no clear instructions on how to do this (at least, none that actually work!). Even the Nextcloud site does not discuss this!

Has anyone successfully migrated a dockerized Nextcloud installation from one machine to another? If so, how exactly was this done?

Was just able to do this myself, although I'm migrating my nextcloud install off my primary home server to a slower NAS-ish box I salvaged together after a move.

The main issues I ran into were file/dir ownership moving from one machine to another. Secondary was ensuring trusted domains were set correctly in config.php

I'm sure it'd be better to use rsync to copy/move files from machine to machine and ensure you keep ownership intact, but I used scp and changed ownership manually. Your nextcloud_data container needs the www-data user to have ownership of the dir you have mapped to /var/www/html and the nextcloud_db (I use mariadb here, YMMV) container needs the systemd-coredump user to have ownership of the dir you have mapped to /var/lib/mysql (or whatever your db backend equivalent is)

Then just make sure you switch over your trusted_domains and trusted_proxies, either using docker-compose env vars, or by editing /var/www/html/config/config.phpdirectly.